Method for plating race-type assemblies

ABSTRACT

A method for converting an assembled, low-carbon-steel bearing of the double-race type of nickel-plated assembly having substantially the same dimensions throughout as the original bearing. The method is conducted with the bearing in the assembled state and comprises modifying all of the bearing surfaces by the steps of degreasing, chemically etching, chemically milling, chemically re-etching, and chemically nickel plating to replace with nickel the amount of metal removed by milling. During all but the re-etching step, relative movement is provided between the bearing races.

Waited States Patent [191 Dalton et a1.

[ METHOD FOR PLATING RACE-TYPE ASSEMBLIES [75] Inventors: James T. Dalton, Knoxville; Ralph R. Wright, Oak Ridge, both of Term.

[73] Assignee: The United States of America as represented by the United States Atomic Energy Commission, Washington, DC.

[22] Filed: Oct. 12, 1973 [21] Appl. No.: 406,050

[52] U.S. Cl 117/50, 29/149.5 MN, 117/130 E,

FOREIGN PATENTS OR APPLICATIONS 1,220,699 7/1966 Germany 117/50 [4 Feb. 18, 1975 OTHER PUBLICATIONS Halls, Acid Pickling Solutions," Metal Finishing, October, 1952,

Symposium on Electroless Nickle Plating, page 46, 1959.

Primary ExaminerMayer Weinblatt Assistant Examiner-John D. Smith Attorney, Agent, or Firm-John A. Horan; David S. Zachry; Fred 0. Lewis [57] ABSTRACT A method for converting an assembled, low'carbon steel bearing of the double-race type of nickel-plated assembly having substantially the same dimensions throughout as the original bearing. The method is conducted with the bearing in the assembled state and comprises modifying all of the bearing surfaces by the steps of degreasing, chemically etching, chemically milling, chemically re-etching, and chemically nickel plating to replace with nickel the amount of metal' removed by milling. During all but the re-etching step, relative movement is provided between the bearing races.

6 Claims, No Drawings BACKGROUND OF THE INVENTION This invention was made in the course of, or under, a contract with the US. Atomic Energy Commission.

This invention relates generally to methods for the electroless nickel plating of steel articles and more particularly to the electroless nickel plating of low-carbon steel bearing assemblies of the kind having both inner and outer races.

Despite the fact that steel bearings of the ball, roller, and needle types are commercially available in a wide range of sizes and as off-the-shelf items, electrolessnickel-plated steel bearings are available only on a special-order basis and thus-at a relatively high unit price. The unit price is even higher if the special order is for only a relatively few plated bearings. This problem could be alleviated, both for the manufacturer and the buyer, if a simple and convenient method were available for converting the off-the-shelf bearings to electroless-nickel-plated bearings of equivalent size.

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a novel method for the production of electrolessnickel-plated, low-carbon-steel bearing assemblies of the double-race type.

It is another object to provide a method for converting an unplated steel bearing assembly to a nickelplated assembly of essentially the same dimensions.

It is another object to provide a novel method for the salvage of steel bearing assemblies which in service have become pitted, worn, or corroded.

It is another object to provide a method for the chemical sizing and electroless-nickel-plating of steel bearing assemblies in the assembled state.

Other objects will become evident hereinafter.

This invention can be summarized as follows:

The method of converting an assembled, low-carbonsteel bearing of the type having inner and outer races to a nickel'plated assembly having substantially the same dimensions throughout as said bearing comprising: degreasing the surfaces of said bearing in the assembled state; chemically etching the surfaces of the resulting degreased assembly; chemically milling the resulting etched assembly to remove from the surfaces thereof a selected amount of metal; chemically etching the surfaces of the resulting milled assembly; chemically nickel plating the resulting milled and etched assembly to replace with deposited nickel the amount of metal removed by said milling; and providing relative movement between said inner and outer races in the course ofthe degreasing, first etching, milling, and plating operations.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT This invention is applicable to the nickel-plating of both new and used double-race-type bearing assemblies of various compositions and sizes. For brevity, however, it will be illustrated below as applied to unused, standard ball bearing assemblies fabricated of low-carbon steel, such as SAE 52100. The phrase lowcarbon-steel is used herein to refer tosteel containing less than about 1 percent carbon. In the following example of the invetion, the various percentages cited are percentages by weight. As is customary, chemically deposited nickel alloy is referred to herein as nickel.

EXAMPLE A ball bearing of the type described above (Bearing No. 2312, SKF Industries, Inc.) was degreased in the assembled state by immersing in ultrasonically agitated methyl chloroform for 5 minutes and then making the assembly anodic in a 12 oz/gal aqueous solution of a conventional alkali-type cleaner (e.g., Anodex U" or Metex 2832, manufactured by McDermid of Bristol, Inc., Bristol, Conn.). The assembly was anodically degreased for 15 minutes at about 195F and a current density of about 0.3 amp. per square inch. Agitation was provided. After degreasing, the assembly was immersed in and agitated in 22% HCl aqueous solution for a period of l-2 minutes at 12.0 130F, to remove rust and mill scale.

After rinsing with water, the bearing assembly was chemically milled under conditions selected to remove 0.0015 inch of metal from all surfaces. Milling was accomplished by immersion for 10 minutes in an aqueous solution containing 3% NH F.HF and 6% H O The solution was maintained at approximately F. At 2 to 5 second intervals during milling, the inner race of the bearing was turned and then stopped suddenly, to reposition the balls, thus permitting uniform etching. After the milling operation the bearing was immersed for 2 minutes in 22%-HC1 aqueous solution (temperature: 122 -130+F) to lightly etch the: metal surfaces. The solution was agitated during etching.

The etched bearing assembly was placed in a hexagonal plating tumbler, and the tumbler immersed in a conventional acid-type electroless nickel plating bath of the kind described in US. Pat. No. 2,532,283, to Brenner and Riddell, to deposit on the bearing surfaces the amount of metal removed during the preceding milling operation. The bath was maintained at 194 -203F. The tumbler was agitated throughout the plating operation to impart relative motion to the bearing races and ensure a uniform deposit of nickel on the balls and races. Once during the plating operation the bearing assembly was removed from the bath, inspected, and the balls repositioned. The desired amount of nickel (-0.00l5 inch) was deposited on the metal surfaces of the assembly in minutes. The assembly so plated was recovered from the bath, rinsed in water, and dried. Cross-sectional metallographic examination of the various surfaces of the plated assembly showed a very uniform and adherent nickel plating having a thickness of essentially 0.0015 inch. The plating had a hardness in the range of 520 -53 on the Rock well C scale, and the surface smoothness of the various components was essentially equal to that of the original assembly. Several hundred runs similar to the run just described were conducted; these established that ball bearings with the desired surface plating and component dimensions could be obtained consistently.

Thus, we have found a convenient method for converting a low-carbon-steel bearing assembly to a nickelplated bearing of equivalent size and smoothness. The method does not involve time-consuming and expensive disassembly and reassembly of the bearing. Neither does it involve machining of the bearing surfaces, which would require subsequent heat-treatment of the machined surfaces. The nickel plate has a relatively low coefficient of friction and is highly resistant to corrosion.

Referring to the various steps of our method, it will be understood that while we prefer to degrease as illustrated above, degreasing can be accomplished satisfactorily by various other techniques well known in the art. For example, a suitable alternative is vapordegreasing in volatile solvents, such as Freon and trichloroethylene. Again, the degreasing can be accomplished in a single step by making the bearing anodic in well-known alkali solutions. Similarly, the two chemical etching steps can be effected by other well-known techniques, as by dipping in conventional rust and scale removers and then activating the steel surfaces by exposing to phosphoric acid. The milling operation can be conducted by any suitable conventional technique, as by contacting the bearing assembly with a mixture of oxalic-acid, sulfuric acid, and hydrogen peroxide. The plating operation can be conducted by conventional techniques and with any standard chemical nickelplating bath characterized by good stability and the deposition of smooth, substantially pore-free, low-stress platings. The determination of the more suitable acid or alkaline baths may require routine testing but is well within the skillof the art.

In the courseof the degreasing operation, the first etching operation, the milling operation, and the plating operation, relative movement is provided between the races of the bearingfThis promotes uniform treatment of all of the surfaces of the bearing. By in the course of is meant intermittently or continuously. The relative movement can be accomplished by various techniques known to the art, as by periodically moving a race manually or by caging the bearing in any suitable tumbling device, such as a hexagonal or octagonal tumbler ofthe kind used in plating operations. Tumbling is optional in the second etching operation, since the preceding milling step has provided appreciable slop between the balls or rollers and the races. Preferably,-the second etching operation is conducted with the solution agitated.

It will be understood that the above-illustrated operating conditions for conducting the various steps of our method are not necessarily the optimum and that it is within the skill of the art to adjust the various parameters, such as temperature, length of treatment time, reactant concentrations, and nickel ion content, to promote efficient operation for a given application. Although our method has been illustrated as applied to unused double-race-type bearings, it is also applicable to restoring used steel bearings to substantially their originaldimensions and surface smoothness. In that application the chemical milling operation is conducted to eliminate pits, etc., before plating. The feasibility of salvaging used bearings in this manner has been demonstrated in some fifty tests conducted with used lowcarbon-steel ball bearings.

What is claimed is:

1. The method of converting an assembled, lowcarbon-steel bearing of the type having inner and outer races to a nickel-plated assembly having substantially the same dimensions throughout as said bearing comprising:

a. degreasing the surfaces of said bearing in the assembled state;

b. chemically etching the surfaces of the resulting degreased assembly;

c. chemically milling the resulting etched assembly to remove from the surface thereof a selected amount of metal;

d. chemically etching the surfaces of the resulting milled assembly;

e. chemically nickel plating the resulting milled and etched assembly to replace with deposited nickel the amount of metal removed by said milling; and

f. providing relative movement between said inner and outer races in the course of operations (a), (b (c), and (e).

2. The method of claim 1 wherein etching operation (b) is conducted in an aqueous solution of hydrochloric acid.

3. The method of claim 1 wherein milling operation (0) is conducted in an aqueous solution of hydrogen peroxide containing fluoride ions and available hydrogen ions. V

4. The method of claim 1 wherein etching operation (d) is conducted in an agitated etching bath.

5. The method of claim 1 wherein plating operation (e) is conducted in an acid electroless-nickel-plating bath.

6. The method of converting an assembled, lowcarbon-steel bearing of the type having outer and inner races, said bearing having as-manufactured dimensions throughout, into a nickel-plated assembly having substantially the same dimensions throughout as said bearing comprising:

a. degreasing the surfaces of said bearing in the assembled state;

b. chemically etching the surfaces of the resulting degreased assembly;

c. chemically milling the resulting etched assembly to remove from the surfaces thereof a selected amount of metal;

d. chemically etching the surfaces of the resulting milled assembly;

e. chemically nickel plating the resulting milled and etched assembly to replace with deposited nickel the amount of metal removed by said milling; and

f. providing relative movement between said inner and outer races in the course of operations (a), (b), (c), and (e). 

1. THE METHOD OF CONVERTING AN ASSEMBLED, LOW-CARBONSTEEL BEARING OF THE TYPE HAVING INNER AND OUTER RACES TO A NICKLE-PLATED ASSEMBLY HAVING SUBSTANTIALLY THE SAME DIMENSIONS THROUGHOUT AS SAID BEARING COMPRISING: A. DEGREASING THE SURFACE OF SAID BEARING IN THE ASSEMBLED STATE; B. CHEMICALLY ETCHING THE SURFACES OF THE RESULTING DEGREASED ASSEMBLY; C. CHEMICALLY MILLING THE RESULTING ETCHED ASSEMBLY TO REMOVE FROM THE SURFACE THEREOF A SELECTED AMOUNT OF METAL; D. CHEMICALLY ETCHING THE SURFACES OF THE RESULTING MILLED ASSEMBLY; E. CHEMICALLY NICKLE PLATING THE RESULTING MILLED AND ETCHED ASSEMBLY TO REPLACE WITH DEPOSITED NICKLE TO THE AMOUNT OF METAL REMOVED BY SAID MILLING; AND F. PROVIDING RELATIVE MOVEMENT BETWEEN SAID INNER AND OUTER RACES IN THE COURSE OF OPERATIONS (A), (B), (C), AND (E).
 2. The method of claim 1 wherein etching operation (b) is conducted in an aqueous solution of hydrochloric acid.
 3. The method of claim 1 wherein milling operation (c) is conducted in an aqueous solution of hydrogen peroxide containing fluoride ions and available hydrogen ions.
 4. The method of claim 1 wherein etching operation (d) is conducted in an agitated etching bath.
 5. The method of claim 1 wherein plating operation (e) is conducted in an acid electroless-nickel-plating bath.
 6. The method of converting an assembled, low-carbon-steel bearing of the type having outer and inner races, said bearing having as-manufactured dimensions throughout, into a nickel-plated assembly having substantially the same dimensions throughout as said bearing comprising: a. degreasing the surfaces of said bearing in the assembled state; b. chemically etching the surfaces of the resulting degreased assembly; c. chemically milling the resulting etched assembly to remove from the surfaces thereof a selected amount of metal; d. chemically etching the surfaces of the resulting milled assembly; e. chemically nickel plating the resulting milled and etched assembly to replace with deposited nickel the amount of metal removed by said milling; and f. providing relative movement between said inner and outer races in the course of operations (a), (b), (c), and (e). 